The output power from a diode laser is known to vary as a function of temperature, natural aging, and drive current. As materials and fabrication techniques have improved, aging has become less of a problem. Temperature variations can be handled either by placing the laser in a controlled environment (oven or refrigerator), or by programming the drive source to correct for temperature variations. This type of control, however, will either require individual adjustment or extremely tight tolerances on design parameters which, in turn, will lead to reduced yield and higher cost.
The third factor referred to hereinabove, i.e., drive current, is particularly important because of the ease with which catastrophic mirror damage occurs in diode lasers when the radiation output power exceeds the critical value. This can occur as a result of spurious fluctuations in the drive current which, in the more efficient diodes, need not be very big.
It is, accordingly, the broad object of the present invention to stabilize the output power from diode lasers.